This proposal includes several diverse projects related to the effects of hormones on bone. The nature of the CO2-HCO minus 3 requirement for bone resorption will be investigated further. Effects of varying CO2, HCO minus 3 and H plus concentrations will be tested and the metabolic steps for which CO2 and/or HCO minus 3 are crucial to resorption will be sought. Purification and characterization procedures will be carried out on a serum albumin constituent which has been found to produce bone resorption. The mechanism of the direct inhibitory actions of glucocorticoids and glucagon on bone resorption will be investigated further. Areas which will be emphasized include effects on protein synthesis, lysosomes, calcium transport and permeability to substances producing resorption. Studies will be carried out to further define direct effects of estrogens, androgens and growth hormone on bone in vitro. These studies include use of modified culture systems more sensitive to calcium accretion as well as modification of the hormonal environment of the resorption system by the addition of substances which may be essential for the expression of the estrogen effects.